Intake grill for water jet pump



Feb 6, 1968 R. c. STALLMAN 3,367,116

INTAKE GRILL FOR WATER JET PUMP Filed Dec. 13, 1965 QINVENTOR. L 49 4e RICHARD c. STALLMAN 5| BY F/G. 9 w /iwt ATTORNEYS United States Patent ()fiFice 3,367,116 Patented Feb. 6, 1968 3,367,116 INTAKE GRILL FOR WATER JET PUMP Richard C. Stallman, 1311 Dayton Sh, Alameda, Qalif. 94501 Filed Dec. 13, 1965, Ser. No. 513,183 2 Claims. (Cl. 613-221) ABSTRACT OF THE DISCLOSURE This invention relates to water jet motor apparatus for boats and more particularly to an intake grill for a water jet pump for a boat motor adapted for ingestion of sand and gravel.

A water jet motor for boats of a type to which the present invention pertains is shown in my U.S. Letters Patent 3,082,732. In the method of propulsion as there shown, the boats engine drives a water pump which forces water, at high volume and pressure, through a nozzle directed astern of the boat. In the nozzle, the mass of water is accelerated and the thrust reaction drives the boat forward. Both an inboard and an outboard motor are shown. An impeller is arranged to spin within a casing whereby water entering the casing is pumped through the nozzle.

When using an impeller operating within a casing and while operating a water jet pump motor in extremely shallow water where sand and gravel may be ingested into the pump, it has been observed that sand and small rocks ingested by the pump can cause erosion of the impeller and casing. This is primarily true in the region of the peripheral clearance between the impeller blades or vanes and the wall of the casing. It is necessary for the impeller to operate with relatively close peripheral clearance with respect to the casing in order to maintain an operational level of pressure as developed by rotation of the impeller.

It has been further observed that the normal generated shape of a so-called open impeller results in a spiral shaped leading edge which forms a wedge-shaped pocket with the casing wall so as to greatly increase the Wear at that point. In the so-called closed type of impeller, a wear ring is used to maintain pressure and thus the bounding surfaces for the clearance between the wear ring and the impeller are the surfaces which are subject to erosion from ingested sand and gravel.

In general, it is an object of the invention to provide an improved water jet pump style of motor for powering boats.

It is a more particular object of the invention to adapt and improve a water jet pump to ingest sand and gravel with minimal deleterious effects whereby the motor can be operated in extremely shallow Waters.

Water jet pump motors of the type described above require a continuous adequate influx of water thereto. Inasmuch as a suction is formed at the intake to such motors, a protective grill work disposed across the intake serves to block the entry of rocks and foreign bodies. Rocks and foreign bodies of a dimension comparable to the open spacing between grill members can become lodged in the grill so as to diminish the cross-sectional area of the flow path into the pump and thereby impair efficient operation.

According to the present invention, a water jet pump is adapted for dislodging and thereafter ingesting rocks lodged in the grill.

Therefore, another object of the invention is to provide a grill having a tendency to inhibit retention of rocks lodged therein.

These and other objects of the invention will be more clearly apparent from the following detailed description of preferred embodiments when considered in conjunction with the drawings in which: 1

FIGURE 1 shows a boat and outboard motor including a water jet motor in accordance with the invention;

FIGURE 2 is a bottom view of a portion of the boat and the jet pump taken along the line 22 of FIGURE 3;

FIGURE 3 is a center line vertical section view of a jet pump and impeller according to the invention adapted for ingestion of sand and gravel;

FIGURE 4 is a sectional view of the impeller shown in the embodiment of FIGURE 3 taken along the line 4-4;

FIGURE 5 is an enlarged detail section view taken along the line 55 of FIGURE 3;

FIGURE 6 is an elevation section view taken along the line 6-6 of FIGURE 3 showing details of the intake grill;

FIGURE 7 shows another embodiment of the invention including a shrouded impeller;

FIGURE 8 is a plan vie-w of another impeller suitable for use in a jet motor; and

FIGURE 9 is an enlarged partial view of another embodiment of the invention including a shrouded impeller.

In FIGURE 1, an outboard motor 1 is shown attached to a boat 2 in the normal manner with suitable clamps 3. The jet pump assembly 4 is suitably attached to the existing flange 5 of the outboard motor with bolts 6. Accordingly, the jet pump assembly replaces the standard outboard motor gear box and propeller section. Water enters the jet pump through an intake section 7 shown also in FIGURE 2, and enters the casing 8. The casing 8 has a tapered upper region 8a which increases in diameter towards the upper end. This section accommodates a mixed fiow impeller 9. The impeller is driven by the drive shaft 10. Engagement with the power-head of the outboard motor is made in the normal fashion by means of an upper spline (not shown) of drive shaft 10. Water discharges from casing 8 into a recuperator 11 and thence through a constricting nozzle.

Impeller 9 is provided with blades or vanes 12 formed integral with or secured to a conical hub 13. The vanes 12 extend outwardly from hub 13, and are in the form of a spiral or screw to move the water as they are rotated. The edges of vanes 12 move with close clearance to the inner wall of casing 8.

Casing 8 includes an open intake end portion including an opening 14. It will be apparent that casing 8 is of the open flow-through type including a flow passage from one end to the other. A resilient liner 16 of suitable material such as rubber is carried on the inner wall of easing 8.

A clearance 15 exists between the outer edges of vanes 12 and the inner wall surface of the resilient liner. It has been observed that water provides an excellent coolant and lubricant between the impeller and the resilient liner 16. As a result, the impeller 9 can be operated with minimal clearance 15. It has been further observed that particles of sand and gravel that enter clearance 15 are momentarily pressed into the resilient material of liner 16 for the instant that the impeller blade passes over them. Thereafter, such particles rebound back into the stream of water and are entrained and carried away.

In order to minimize the wedging of rocks between the inner surface of liner 16 and the leading edges of vanes 12, the leading edges of the vanes may be formed along radial lines rather than curved as shown in FIGURE 4. The embodiment of the impeller shown in FIGURE 8 includes such vanes 12a. It is seen that they move continuo'usly disposed at substantially right angles to the rebounding layer formed by liner 16. Thus, rocks, sand, etc., being struck by the leading edge of vanes 12a are impelled along the surface of liner 16 rather than being wedged against it to rebound. The rocks, sand, etc., are entrained and carried away by the water flowing through casing 8.

Liner 16 is preferably bonded to a rigid backing member 17 which is readily removable from casing 8 as by means of the dual lock screws 18 threadedly passing through the wall of easing 8 via a threaded opening partially extending into member 17.

An intake grill assembly having a tendency to inhibit retention of rocks wedged therein extends across intake opening .14 and comprises a plurality of elongated bars 21 set on edge to present a minimum resistance to flow of water via opening 14. Bars 21 are carried in slots 22 formed in the bottom of casing 8 on opposite sides of opening 14. Bars 21 are retained in slots 22 by means of cross pins 23 which extend transversely through enlarged holes 24 in the opposite ends of each bar.

Holes 24 are dimensioned with respect to the associated pin 23 (which extends through it) to be sufliciently large to permit bars 21 to tip slightly from side to side for purposes as will be explained further below. Accordingly, the dimension of slots 22 provides adequate clearance to accommodate this tipping or wobbling movement.

As shown best in FIGURE 6, each of the bars 21 is formed with a transverse cross section of trapezoidal configuration whereby each bar is characterized by relatively broad sides 26, 27 lying generally parallel to the flow of water entering intake opening 14 and edges comprising relatively narrow sides 28, 29. Sides 28, 29 lie transversely of the direction of water flow in a flow impeding position. The broad sides 26, 27 of adjacent bars 21 which are disposed in confronting relation to each other diverge in the downstream direction to gradually enlarge the spacing between adjacent bars in the direction of flow through casing 8.

From the foregoing, it will be apparent that each bar 21 is formed with a trapezoidal transverse cross-section throughout that portion of its length which extends across the open intake portion defined by opening 14. The parallel sides of the trapezoid form the narrow sidesof each bar.

Rocks and foreign bodies generally larger than the spacing between bars 21 cannot enter pump assembly 4 whereby harm would be caused the impeller. Rocks smaller than the spacing between bars 21 enter easily and pass harmlessly through the pump. Thus, the spacing between bars 21 serves to limit the size of rocks and foreign bodies ingested into the pump to a maximum predetermined size which is considered not to be harmful to the impeller.

Those rocks having a dimension corresponding sub= stantially to the spacing between bars 21 tend to lodge between the bars and if not removed can serve to diminish the effective cross-sectional area of the flow passage through casing 8. However, as shown in FIGURE 6, the ever widening spacing defined between adjacent bars 21 in the direction of fluid flow as provided by the ever diverging confronting broad sides of bars 21, serves to readily release this troublesome size of rocks and foreign bodies.

The ends of bars 21 are loosely supported to permit them to tip or wobble about an axis 31. Whenever a rock becomes lodged between adjacent bars 21, the bars will tip or wobble slightly to further Widen the spacing in the downstream direction.

From the foregoing, it will be readily apparent that when a rock which might otherwise become lodged between bars 21 begins its passage between adjacent bars, the downstream sides 28 of the adjacent bars will be pivoted apart. By virtue of the fact that the confronting broad sides 26, 27 of adjacent bars diverge in an ever increasing spacing, the rock will continue on through the grill.

According to another embodiment of the apparatus, as shown in FIGURE 7, a so-called closed style of impeller 41 is disposed for rotation within a casing 42 of a flowthrough type casing as described above. As noted above, clearance between the impeller and easing must necessarily be relatively close in order to maintain an operative level of pressure within the casing. Where a closed impeller is employed as in FIGURE 7, the bounding surfaces of the clearance 43 are subject to considerable deterioration under action of sand ingested into the pump. It has been observed that provision of a resilient wear ring 44 encircling impeller 41 serves to minimize wear and abrasion caused by sand and small particles encountering clearance 43. The outside wall of impeller 41 is formed with an encircling shroud 46.

In operation, sand which enters clearance 43 rebounds from a bounding surface thereof where it can be carried by a small flow of water through the clearance 47 defined between impeller 41 and casing 42 until it is again entrained by the mainstream of fluid passing through casing 42.

According to another embodiment, as shown in FIG- URE 9, the resilient wear ring 44 of FIGURE 8 can be carried by shroud 46. Thus, wear ring 49 defines a bounding surface to clearance 51 formed between the intake end of impeller 41 and casing 42.

I claim:

1. In a water jet pump of the type adapted for use in a boat motor to drive a boat through the water, a flowthrough casing having an open downstream end portion and an open intake end portion, said portions defining a flow path through said casing, a mixed flow impeller axially mounted for rotation within said casing and defining between the periphery of the impeller and the inner wall of the casing a sufficiently limited radial clearance to maintain operational pressure developed by rotation of the impeller, and a layer of resilient material forming a bounding surface to said clearance and encircling said impeller, a grill comprising a plurality of bars supported in spaced substantially parallel disposition across said intake portion of the casing, each of said bars being characterized by relatively broad sides and relatively narrow sides, said narrow sides lying transversely of thedirection of water flow through the casing in fiow-impeding position and the broad sides lying generally parallel to said flow in flow-passing position, the broad sides of adjacent bars being disposed in confronting relation to each other, and means for mounting the bars for independent wobbling movement about an associated axis extending generally parallel to all said sides to wobble responsive to the lodging of a rock between adjacent bars to act to dislodge said rock, said layer of resilient material being disposed to thereafter rebound those rocks and foreign bodies passing through said grill vanes into the flow of water moving through the casing.

2. In a water jet pump of the type adapted for use in a boat motor to drive a boat through the water, a flowthrough casing having an open downstream end portion and an open intake end portion, said portions defining a flow path through said casing, a grill comprising a plurality of elongated bars supported in spaced substantially parallel disposition for limiting the size of rocks and foreign bodies ingested by the pump to a predetermined maximum size, said bars being disposed across said intake portion of the casing, each of said bars being characterized by relatively broad sides and relatively narrow sides, said narrow sides lying transversely of the direction of Water flow through the casing in flow-impeding position and the broad sides lying generally parallel to the flow in flowpassing position, the broad sides of adjacent bars being disposed in confronting relation to each other, and means for mounting each bar to tip about an axis extending generally parallel to all said sides.

References Cited UNITED STATES PATENTS TaWara 60-221 Austin 1150.5 Dahle 6022l X Stallman 6( 221 X Hamilton 60222 X Irgens 60-221 X Patton 1150.5

CARLTON R. CROYLE, Primary Examiner. 

